The present disclosure relates to a developing device for developing an electrostatic latent image formed on an image bearing member using magnetic one-component developer and an image forming apparatus provided with this developing device.
Conventionally, a developing device as described below is known as a developing device used in an image forming apparatus such as a printer and configured to develop an electrostatic latent image formed on an image bearing member using magnetic one-component developer. Such a developing device includes a rotary sleeve including a fixed magnet therein and a toner layer thickness restricting member for restricting the thickness of a toner layer formed on the rotary sleeve. The toner layer thickness restricting member includes a blade formed of a magnetic plate-like member and a magnet mounted on an upstream side of this blade in a rotation direction of the rotary sleeve.
In the above technology, out of the fixed magnet inside the rotary sleeve, a magnetic pole having the same polarity as the magnet of the toner layer thickness restricting member is arranged at a position facing the toner layer thickness restricting member. A thin layer of toner can be formed by the magnets having the same polarity facing each other in an area where the toner layer is restricted. As a result, toner charging is improved and image quality defect such as fogging is suppressed.
When the magnets having the same polarity are arranged to face each other and a thin layer of toner is formed by a repulsive magnetic field in restricting the layer of the magnetic one-component developer as described above, the conveyance of toner may become unstable. In this case, an unstable state of conveying the toner on the rotary sleeve leads to uneven toner supply to the image bearing member. As a result, image defects such as longitudinal streaks may be caused in a printed image.
The present disclosure was developed to solve the above problem and aims to prevent a failure in conveying developer in restricting a layer of magnetic one-component developer.